VPC and Subnets CIDR Best Practices?


I've always used /16 CIDR for VPCs. Example: VPC - Subnets for 250 available hosts. Is there a recommended VPC segmentation best practice? Is there a best practice to follow when creating subnets CIDRs? I know it depends on how many IP addresses I need in my subnet, but besides that, is there any other thing to consider before the VPC and Subnets creation? Thank you!

3 Answers


There are some general guidelines you can find here: https://docs.aws.amazon.com/quickstart/latest/vpc/architecture.html

Every environment is different, you should consult with your AWS Solutions Architect for specific guidance.

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answered 2 months ago

I've always used this reference document. It's a great little "Cliff Note" of VPC Design.

answered 2 months ago


There are several approaches to consider when implementing an AWS VPC in an AWS account. In addition to this, some important things to consider are flexibility between and outside of AWS accounts.


1/ When you consider your disaster recovery plan, you must ensure that there is no overlap or conflict with your local subnet CIDR.

2/ When you want to advertise a Virtual Private Cloud (Amazon VPC) route to your on-premises network through an AWS Direct Connect VIF BGP session, you can consider the longest/shortest VPC CIDR prefix to decide the route.

3/ VPC peering is also the point where you want to connect two Amazon VPCs

Hope it helps.

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answered 2 months ago

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